PSN Sub Accounts Can Now Be Upgraded to Master Accounts

As of today, PlayStation Network users with sub accounts can upgrade to master accounts and transfer over their profiles.

The announcement comes by way of the PlayStation Blog,
who reports that these account upgrades can only be done through the
web at this time. The ability to upgrade through the PlayStation 4 is
expected to arrive in the future. Visit the official upgrade page to learn more about the process.

Used to help monitor and limit PlayStation usage for players under 18,
sub accounts restrict access to several components of the PlayStation
Network, including messages, monthly spending limits, and broadcasts.
Once upgraded, they will be able to access all features in a standard
master account. It should be noted that users must be at least 18 years
old to be able to upgrade.